This application claims priority to United Kingdom Application No. GB 0013064.1 filed May 31, 2000.
The present invention relates generally to motorised drive or actuation mechanisms and in particular to selectively engagable drive or actuation mechanisms which are particularly suitable for providing multiple selective drive or actuation means. Specifically, although not exclusively, the invention relates to a drive mechanism which is suitable for automotive applications and in particular to providing a multiple selective drive and actuation mechanism for an adjustable seat.
Various motorised drive or actuation means are generally well known. Such means often comprise a motor which rotates shafts, lead screws, gears, worms gears or other transmission means in order to provide motive power to a particular mechanism, or to move a member. There are numerous such arrangements and there is a constant desire to provide improved simplified, robust, reliable and cost effective motorised drive means.
With such motorised drive means it is generally required to be able to selectively operate the drive means. Selective movement of the mechanism or member driven by the motor is typically controlled by controlling and switching the power to the motor. Consequently if multiple motorised drive and actuation means are required, which are independently operable and are to be independently selectable, then separate motors and drive means are generally provided which may be individually controlled. Consequently many motors and separate control means are required. This is costly and generally undesirable.
Within the automotive field and within automotive vehicles there are numerous, and an increasing number of, applications of motorised drive means and multiple, independently selectable drive means.
In particular it is common for vehicle seats to be increasingly adjustable in a number of different ways. For example vehicle seats may be required to slide relative to the vehicle in a forward and rear direction (track), to be raised and lowered (lift), to tilt (tilt), and/or for the seat back to recline (recline). Other adjustments may also be required. Increasingly such seat movements and adjustments are required to be motorised. Conventionally individual motors connected to suitable mechanical transmission and adjustment mechanisms have been used within the seat assembly to provide the required motorised adjustment. Each of the individual motors is controlled by separate switches and control means. The use of multiple motors is costly and is generally undesirable, especially as the number of independent motorised adjustable drives required for a seat, and so motors required, increases. Furthermore as the number of motorised seat adjustments increases it is increasingly difficult to install the increasing number of individual motors conventionally required.
Another automotive application where multiple selectable drive means are required and used is for motorised wing or door mirror adjustment. Again multiple individual motors are generally used. There are also a large, and increasing, number of other applications of multiple selectable motorised drive means within the automotive field. Furthermore there are other similar such applications in other fields.
It is therefore desirable to provide an improved selective drive mechanism which addresses the above described problems and/or which offers improvements generally. In particular it is desirable to provide a simple and effective selective drive mechanism which is cheap and simple to manufacture. It is also desirable to provide a simple multiple drive arrangement which similarly is cheap tp produce and provides multiple drive to a number of adjustment mechanisms.
According to the present invention there is provided a selective drive mechanism as described in the accompanying claims.
In an embodiment of the invention there is provided a selective drive mechanism comprising a driven drive shaft, a drive nut/drive element disposed about the drive shaft and which is adapted to be selectively driven by the drive shaft, a locking means associated with the drive nut and drive shaft, and an operable control arm which selectively engages with and operates the locking means. The locking means comprising a coil, helical spring coaxially mounted about the drive shaft. The mechanism is arranged such that with the control arm in a first position the locking means is arranged to lock the drive nut to the drive shaft so that the relative positions of the drive nut and drive shaft are fixed. However with the control arm in a second position the locking means drive nut and drive shaft are arranged so that the drive nut can and is moved relative to the drive shaft.
Accordingly the mechanism provides a simple and effective means for providing a selective drive from a driven shaft with the drive only being provided and the mechanism only engaging the driven drive shaft when selected by movement of the control arm. In this arrangement the drive element is also in both modes of operation engaged and located on the driven shaft. As such the drive element/nut is positively located during both modes of operation.
Furthermore such a selectable drive mechanism is particularly suitable and advantageous for use in providing a multiple selective drive mechanism.
In effect the mechanism of the present invention is, and provides, a selective clutch type means to selectively provide and output drive from a drive shaft in response to the clutch (selective drive mechanism, and specifically the control arm) being operatively engaged by an operator.
Preferably there may also be provided in an embodiment a multiple selective drive mechanism comprising at least two operatively selective drive mechanisms of the type described above, in which a common drive shaft comprises the drive shaft of each of said at least two selective drive mechanisms.
With such a mechanism a multiple selective drive can be provided from a single driven shaft. This advantageously means that only one motor is required to drive the common shaft in order to provide a multiple selective drive arrangement and mechanism.
The selective drive mechanism described, and in particular the multiple selective drive mechanism, is particularly advantageous for use within the automotive field and for providing a selective drive means for components of an automotive vehicle. In particular, and for example, it is particularly advantageous for providing a multiple drive means for a vehicle seat. This is because, at least in part, because the mechanism is particularly adaptable, is of a relatively small size, and can easily be integrated into a vehicle. Accordingly it provides a vehicle designer with increased flexibility, in particular when compared to drive mechanisms involving the use of multiple individual motors. As a result the designer can more easily incorporate the drive mechanism into the vehicle and the drive mechanism and user operating controls (control arm) can be conveniently sited in relation to a user or occupant.
In the automotive field cost and reliability are also key specific considerations, possibly even more so than in some other fields. The proposed mechanism addresses both of these concerns, as compared to prior arrangements especially those using multiple individual motors. It will also be appreciated that drive mechanisms for use with vehicle seats have to be able to withstand high loads and in particular high loads generated during impacts. The mechanical selective locking arrangement of the present invention provides an effective possible means for handling such loads. The mechanical locking also does not rely upon the limited strength or robustness of a motor which may be limited or require specification of a larger motor to handle the high maximum impact loads. These and other advantages, as well as the specific peculiar requirements of the automotive field make the invention particularly, although not exclusively, suitable for such use.